The engine immobiliser system is designed to prevent the vehicle from being stolen. This system uses a transponder key ecu that stores the key codes of authorized ignition keys. If an attempt is made to start the engine using an unauthorized key, the ecu sends a signal to the ecm to prohibit fuel delivery and ignition, effectively disabling the engine.

The transponder key coil receives this signal, the transponder key amplifier amplifies it, and then the signal is transmitted to the ecu. The ecu matches the key's id code with the vehicle's id code, which was previously registered in the ecu and then communicates the results to the ecm using sfi communication.
Engine immobiliser system
How to proceed with troubleshootingCheck 4wd control ecu (for 4wd)
Notice:
Turn the ignition switch off before measuring the
resistances of the main wire and branch wire.
After the ignition switch is turned off, check that the
key reminder warning system and light reminder
warning system are not in operation.
Before measuring the resistance, leave the ...
Unlock warning switch
Inspection
Inspect unlock warning switch assembly
Measure the resistance of the switch.
Standard resistance
If the result is not as specified, replace the switch
assembly.
Ecu power source circuit
Description
This circuit provides power to operate the transponder key ecu.
Wir ...
Only rear door rh lock / unlock functions do not operate
Description
The main body ecu receives lock / unlock switch signals and activates the
door lock motor accordingly.
Wiring diagram
Inspection procedure
Inspect rear door with motor lock assembly rh
Apply the battery voltage to the door lock motor and
check the operation of th ...